Electric furnace.



J. L. DIXON.

ELECTR IC FURNACE. APPLICATION FILED APR. 10. 1916.

1,1 97,458. I Patented Sept. 5,1916.

3 SHEETSSHET lanuenloz ELECTRIC FURNACE. APPUCATION FILED APR.10,1916.

1,197,458. Patented Sept. 5,1916.

3 SHEETS-SHEET 2.

. anuenfoz W WWW J. L. DIXON.

ELECTRIC FURNACE.

APPLICATION FILED APR. 10, me.

1 1 97,45 8 Patented Sept. 5, 1916.

UNITED STATES. PATENT OFFICE.

.zosurn mwron mxon, or DETROIT, MICHIGAN.

ELECTRIC rumucn.

' Specification of Letters Patent.

Patented Sept. 5, 1916.

Original application filed, February 28, 1915, Serial 1T0. 9,782. Divided and this application filed April 10,

' 1916. Serial m. 90,031.

To all whom it-may concern Be it known that I, Josnrrr L. DIXON, a

- of electric smelting furnaces wherein the current may be made to pass either from one electrode to another over the bath or from one or more of these either wholly or in part through the bath and furnace lining.

i so

The/ object of my invention is to supply an improved construction for electric smelting furaces of this kind, whereby twophase currents, fed from specially arranged transformers, are made controllable as to their phase relations by suitable switches, so as to cause different proportions of the total current to flow through the bath and lining.

It is a further object of the invention to accomplish these ends without unbalancing the load on the feeding means.

Certain preferred embodiments of the invention are illustrated diagrammatically in the accompanying drawings'wherein Figure 1 shows a furnace having two pairs of upper electrodes supplied with twohase alternatingvcurrent, Figs. 2 to 8 inc usive are vector diagrams illustrative of altered phase conditions produced by various changes in the electric connections shown in Fig. 1, Fig. 9 illustrates a modified form wherein six upper electrodes are employed,

and Figs. 10 and 11 are vector diagrams 1ndicating different phase relations roducible in the form of furnace shown in ig. 9.

In Fig. 1 the usual hearth, crucible or container is shown at 10, the molten bath .within it is shown at 11, while the four upper electrodes 12,- 13, 14 and 15, roject downward toward the bath through t e insulating cover 16. The current which passes downward through the bath, when so desired, returns through the lower electrode 17 The working current is derived from the threehase alternating current means 18, 19 an 20, being directly sup lied from the low voltage secondaries of t e four transformers 21,22, 23 and 24, in the form of two-phase current. Considered by themselves, the transformers 21 and 22 may be describedas two Scott-connected transformers, delivering secondary currents according to a' system known as the two phase-three wire system. For this purpose the primaries of these transformers. are connected to each other and to the feeding mains'in the well known manner shown, while the lower voltage secondaries have their outer-terminals connected respectively to the upper elec trodes 12 and 13, and their inner terminals connected in common to the lower electrode 17 .The second pair of transformers 23 and 24 are similarly connected to the mains and the furnace electrodes 14, 15 and 17 respectively; save that the wires leading to the mains are connected thereto by means of separate multiple switches 25 and 26. By means of these switches the connections of the transformers'23 and 24 may be reversed with respect to twoof the three feeding or main-wires. When the switch 26 is closed (the switch 25, of course, beingop'en) the transformers 23 and 24are connected. to the mains 18, 19, 20, in a reverse manner with relation to the connections of the transformers 21 and 22. When connected thus, the

phase relations existing in the four upper electrodes are as indicated in Fig. 2; that is to say the phases in the upper electrodes 12 and 14 are 180 degrees apart, as are also those in electrodes 13 and 15. Therefore, if; I

the four currents are of equal magnitude" thereis no current passing through the bath to the lower electrode 17.

'The'precise connections of the ers 23 and 24 as shown in Fig: 1. are merely transform-.

an example of the possibilities of the system.

Forinstance if (with the switch 26 closed) only one instead of both of the primaries of 23 and 24 is reversed with respect to the corresponding transformer 21 or 22, the secondary currents will have'the phase relation shown in Fig; 3, in which case the current through the ath will be equal to 2; unity being the current in each of the, upper electrodes (it being assumed that these are all kept equal). By another obvious change in connections, the relation' of phases shown in Fig. 4 is obtained. In'this case the current through the bath and lower electrode will be 2.82. If, now, in Fig. 1, the switch 25 is y 1'5 l phase relations becomes available, with a shown in Fig. 5 will result. In this case the current through the bath will be 73. Starting from this position and reversing one or' more ofthe phases by appropriate changes in connections we may obtain the phase relations shown respectively in Figs. 6, 7, and, 8. In these cases the current through the bath amounts tolxl, to 2.73 and to 2.45 respectively. It is thus apparent that, 'by using two multiple switches as shown, any two of the seven phase relations shown in Figs; 2 to 8 may be obtained. By increasing the number of switches 'Wltll varied connections a greater number of correspondingly greater number of current values through the bath and lower electrode.

In Fig. 9 is shown another embodiment of the invention suited to a larger furnace,

- having an increased capacity and furnished with six instead of four upper electrodes. These electrodes are numbered 27 28,29, 30, 31 and 32, and are directlysupplied with two-phase alternating current from six transformers, 33, 34, 35, 36 37 and 38 connected in pairs as shown. Two ofthese pairs are permanently Scott connected to the mains 18, 19 and 20, on their primary side; while the primaries of the third pair are similarly connected to said mains through two multiple switches 39 and 40, each having preferably'four'movable switch members, and the innermost movable members of the two sets being permanently connected to each other and -to the middle of the primary 38. As before, the low voltage secondaries of all the transformersare connected by the two-phase three wire system to their respective pairs of upper electrodes. When the switch 40 is closed the phase relations are such as are shown in the vector diagram, Fig. 10. In this case, if the upper electrodes are supplying currents of equal magnitudes among themselves, there will be no current through the bath and lower electrode.

Obviously, a great number ofvariations in. phase relations can be here produced by reversals of the connections of the individual transformers, and a correspondingly great variation is possible in the amount of current which is made to pass through the bath. These changes are all consistent with keeping the current magnitudes equal among the upper electrodes. This variety of phase relations can be still further increased by making changes in connections other than simple reversals. If now the multiple switch be opened and switch 39 closed, the phase relations produced are those shown in Fig. 11; and if the currents are kept equal to unity in each of the six upper electrodes,

the value of the current through the bath and lowerelectrode will be .73.

While, for purposes of simplicity, I have shown only furnaces with four and with six upper electrodes, it is to be understood that the invention covers the use of any number of pairs greater than one.

This application is a division of my earlier application for improvement in electric furnaces, filed February 23, 1915, Serial No. 9782.

What I claim is 1. An electric furnace havinga lower electrode and a plurality of pairs of upper electrodes, feeding mains adapted to supply alternating current, a pair of transformers for each pair of upper electrodes, each pair havingits outer secondary terminals connected with appropriate upper electrodes and its inner terminals connected in. common with the lower electrode, and the primary of each pair of transformers being connected with said mains; and multiple switches for chang ing the current phases in some of the coils of one of said pairs of transformers.

2. An electric furnace having a lower electrode and a plurality of pairs of upper elec trodes, feeding mains adapted to supply threephase alternating current, a pair of Scott-connected transformers for each pair of upper electrodes, each pair having its outer secondary terminals connected with appropriate upper electrodes and its inner secondary terminals connected with the lower electrode, -suitable conductors for connecting the primaries of said transformers with said feeding mains and switches in circuit with said last named conductors adapted to alter the current phases in some of the coils of one of said pairs of transformers.

3. An electric furnace havinga lower electrode and a plurality of pairs of upper electrodes, feeding mains adapted to supply three phase alternating current, a pair of Scott-connected transformers for each pair of electrodes, each pair being connected on its secondary side by the two-phase three wire system to said furnace, and on its primary side with said feeding mains, and two three-part multiple switches with suitable connecting conductors, adapted to alter the current phases in some of the coilsof one of said pairs of transformers.

4. In an electric furnace equipment of the class described, alternating current feeding mains, a number of pairs of transformers having permanent connections with said mains, and an additional pair of similar transformers intended to have its feeding connectionsv altered; in combination with switches and connecting conductors suitably arranged to accomplish alteration of current phases in some of the coils of said the various coils of said additional transformer so as to alter the current phases some of the coils trereof.

. In testimony whereof. I have aifixed my signature.

JOSEPH LAWTQN DIXON. 

